Numerical investigation of the influence of volcanic facies architecture on hydrothermal fluid migration: Example of the Mount Read Volcanics, western Tasmania, Australia

Abstract

A 2-D numerical conceptual model is developed to represent the volcanic facies architecture of part of the submarine Mount Read Volcanics successions in western Tasmania. Numerical results reveal that a synvolcanic fault strongly controls fluid migration paths. The pumice and volcanic breccias are also important, focusing hydrothermal fluid circulation and implying that alteration and mineralization may occur preferentially in such facies. As expected, the synvolcanic intrusion significantly alters the pre-existing regime of fluid flow and temperature distribution. Vigorous fluid circulation is initiated near the intrusion and then shifts to the more permeable host facies. Temperature contours diffuse outwards from the heat source. The intrusion becomes less important with time due to the energy loss by heat conduction and convection. Fluid migration along the synvolcanic fault reveals an important reversing phenomenon: hydrothermal fluid initially travels upwards then downwards and finally upwards again as the intrusion cools.